The invention relates to a method for processing elastomers, in particular PSA (Pressure-Sensitive Adhesives) made of elastomers, cf. “pressure-sensitive adhesives and applications” Istvan Benedek, Edition 2004, pages 161 et seq. The most frequently used elastomers are rubbers. However, styrene-butadiene polymers or acrylic polymers are also used. Such products have to be initially masticated before they can be blended with other materials. To masticate these elastomers, it is known to process them mechanically and/or chemically. Elastomers possess different characteristics that depend on their origin and basis. The higher the molecular weight of the elastomer, the more difficult the mastication becomes. Mastication is required in order to blend in additives, and also to be able to discharge the elastomers through a die.
In the past, kneaders have been used for the mastication. With kneaders the molecular weight of the elastomers is greatly reduced by severe mechanical deformation in the presence of oxygen and with strong heating. However, the properties of the elastomers are greatly modified by the reduction in the molecular weight, thereby leading to an increasingly difficult production of the adhesive.
Moreover, the kneaders operate only in a batch mode. The kneaders possess a housing, in which one or more mixing arms move. In order to provide a continuous material flow with kneaders a plurality of kneaders are required which continuously provide masticated elastomers.
The mastication may be supported by chemical agents. The chemical agents are generally undesirable after mastication. Their separation and removal from the resulting material is complex and difficult. Frequently the chemical agents partially remain in the material and impair its quality.
Planetary roller extruders have recently been recommended for the mechanical processing. The planetary roller extruder provides an unequalled gentler treatment of the elastomers in comparison to a kneader or conventional rollers. In the kneader and on conventional rollers the temperature cannot be controlled as well as in the planetary roller extruder. In the kneader and on conventional rollers the ambient air has unimpeded access, such that a considerable number of broken-down molecular structures can bond with the oxygen from the air, thereby creating a considerable disadvantage for subsequent processing of the elastomers.
Moreover, a planetary roller extruder is inherently designed for continuous operation, thereby obviating the need for a plurality of kneaders operating in parallel to produce a continuous material flow.
A planetary roller extruder possesses a central spindle, an inner-toothed housing, and various planetary spindles between the inner toothing of the housing and the planetary spindle. The planetary spindles mesh with both the central spindle as well as with the inner-toothed extruder housing. In this regard the planetary spindles rotate around the central spindle. Inside the housing is a thin liner that is equipped on the inside with toothing and is heated or cooled on the outer side. For this, a tempering fluid is fed along the exterior of the liner. Moreover, the central spindle may also be provided with a temperature control.
The processing of the elastomers and their blending with other substances can be substantially influenced by the type and number of the planetary spindles.
In regard to the details and variations of known planetary roller extruders and their sections/modules, reference is made to the following publications: DE102005007952A1, DE102004061068A1, DE102004038875A1, DE102004048794A1 DE102004048773A1, DE102004048440A1 DE102004046228A1, DE102004044086A1, DE102004044085A1, DE102004038774A1, DE102004034039A1, DE102004032694A1, DE102004026799 B4, DE102004023085A1, DE102004004230A1, DE102004002159A1, DE19962886A1, DE19962883A1, DE19962859A1 DE19960494A1, DE19958398A1, DE19956803A1, DE19956802A1, DE19953796A1, DE19953793A1.
Degassing procedures are described in some of the publications. Partial or complete degassing releases unwanted gas from the material enclosed in the extruder.
Other degassing procedures are described in the following publications: DE102004061185A1, DE102004060966A1, DE102004053929A1, DE1020040050058A1, DE102004004237A1, DE69908565T2, DE69827497T2, DE69807708T2, DE69725985T2, DE69715781T2, DE69715082T2, DE69711597T2, DE69710878T2, DE69709015T2, DE69707763T2, DE69630762T2, DE69628188T2, DE69622375T2, DE69428309T2, DE69427539T2, DE69419146T2, DE69312852T2, DE69312246T2, DE69306874T2, DE69207369T2, DE68928567T2, DE68915788T3, DE60206271T2, DE60012108T2, DE19956483A1, DE19954313A1, DE10257377A1, DE10356821A1, DE10354546A1, DE10354379A1 DE10352444A1, DE10352440A1, DE10352439A1, DE10352432A1, DE10352431A1, DE10352430A1, DE10351463A1, DE10349144A1, DE10345043A1, DE10343964A1, DE10342822A1, DE10340977 B4, DE10340976 B4, DE10333927A1.
A single extruder may be sufficient for a continuous processing in the extruder. The modern modular design advantageously enables a plurality of identical or different modules to be assembled one behind the other, thereby permitting the material to be processed in a desired manner.
With the materials considered here, the mechanical processing is a significant component of the material processing. In this regard the material is repeatedly rolled out between the intermeshing rolling teeth of the planetary roller extruder. The large number of roller operations is due to the number of revolutions of the central spindle and the thus dependent revolutions of the planetary spindles. The material is thus very thinly rolled out dependent on the toothing. This causes an intensive kneading of the material. This kneading masticates the solid material, such as for example rubber, which is fed in particulate form to the planetary roller extruder.